1. Field of the Invention
This invention relates generally to an industrial process, and, more particularly, to a method and apparatus for dispatching based on metrology tool performance in a semiconductor device manufacturing environment.
2. Description of the Related Art
There is a constant drive within the semiconductor industry to increase the quality, reliability and throughput of integrated circuit devices, e.g., microprocessors, memory devices, and the like. This drive is fueled by consumer demands for higher quality computers and electronic devices that operate more reliably. These demands have resulted in a continual improvement in the manufacture of semiconductor devices, e.g., transistors, as well as in the manufacture of integrated circuit devices incorporating such transistors. Additionally, reducing the defects in the manufacture of the components of a typical transistor also lowers the overall cost per transistor as well as the cost of integrated circuit devices incorporating such transistors.
Generally, a set of processing steps is performed on a wafer using a variety of processing tools, including photolithography steppers, etch tools, deposition tools, polishing tools, rapid thermal processing tools, implantation tools, etc. One technique for improving the operation of a semiconductor processing line includes using a factory wide control system to automatically control the operation of the various processing tools. The manufacturing tools communicate with a manufacturing framework or a network of processing modules. Each manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface which facilitates communications between the manufacturing tool and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script based upon a manufacturing model, which can be a software program that automatically retrieves the data needed to execute a manufacturing process. Often, semiconductor devices are staged through multiple manufacturing tools for multiple processes, generating data relating to the quality of the processed semiconductor devices. Pre-processing and/or post-processing metrology data is supplied to process controllers for the tools. Operating recipe parameters are calculated by the process controllers based on the performance model and the metrology information to attempt to achieve post-processing results as close to a process target value as possible. Reducing variation in this manner leads to increased throughput, reduced cost, higher device performance, etc., all of which equate to increased profitability.
Typically, metrology tools, even tools of the same type and model, have differing precision capabilities. These differences may be caused by various factors, including noise, calibration frequency and accuracy, and inherent tool characteristics. Certain processes in a fabrication facility require high measurement precision. If the precision of the metrology data is not sufficiently high the efficacy of process control or fault detection may actually be reduced by a metrology update, rather than increased. For example, the error in the metrology data may actually cause a process controller to errantly shift its operating settings in such a way that variance is increased.
Typically, when metrology is required for a particular lot, all of the available tools are identified and the lot is assigned to one of the tools based on availability. Because the tools may have varying precision characteristics that are not incorporated into the scheduling decisions, situations may occur where the most precise tools are tied up for metrology events that do not require the higher level of precision. These lots may be then assigned to other metrology tools that are available, but have a lesser degree of precision. As a result the usefulness of the metrology data collected for process control or fault detection may be reduced. Subsequently, process control activities may not be effective and/or errant fault detections may be identified. In general, these situations reduce the efficiency and profitability of the fabrication facility.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.